JPH06261546A - Switching power source apparatus - Google Patents

Abstract

PURPOSE:To suppress recovery of a rectifying diode by preventing spike voltage current accompanying switching to suppress a variation in operating frequency accompanying a variation in load, and by improving output stability in a multioutput converter to enlarge the degree of design freedom and to make current resonance. CONSTITUTION:The primary winding of a first transformer 3 having at least a primary winding 3a and one or more secondary windings 3b and a first switching means which repeats on and off states are connected in series, and a series circuit of a second switching means which repeats on and off states alternately with the first switching means and a first capacitor 6 is connected in parallel with the primary winding 3a of the first transformer 3. A series circuit of the primary winding 10a of a second transformer 10 having at least a primary winding 10a and one or more secondary windings 10b is connected in parallel with the second switching means, and voltage generated in the secondary windings 3b, 10b of the first and second transformers 3,10 is supplied to the output via a rectifying smoothing means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device for supplying a regulated DC voltage to industrial and consumer electronic devices.

[0002]

2. Description of the Related Art In recent years, switching power supply devices have been strongly required to be smaller in size, more stable in output, and more efficient, as electronic devices have become lower in price, smaller in size, higher in performance, and more energy efficient.

A conventional switching power supply device will be described below. FIG. 9 shows a conventional switching power supply device, Z
FIG. 3 is a circuit configuration diagram of an input / output non-inverting buck-boost converter called an ETA converter. In FIG. 9, 1 is an input DC power supply, and its voltage is V _IN . 2a-2b are input terminals, to which the input DC power supply 1 is connected. 4 is a switching element, 21 is a first choke coil, and 6 is a capacitor. The switching element 4 converts the input DC voltage V _IN into a high frequency AC voltage,
It is transmitted to the first choke coil 21 and the capacitor 6. The capacitance of the capacitor 6 is sufficiently large, and its voltage holds the DC voltage V _{C in the} direction shown in FIG. 22 is a diode. Reference numeral 23 denotes a second choke coil, which can be magnetically coupled to the first choke coil 21 with the polarity shown in FIG. 12 is a smoothing capacitor, 1
3a-13b are output terminals. The electrostatic capacitance of the smoothing capacitor 12 is sufficiently large, and the output voltage V _O is output to the output terminals 13a-13b. Reference numeral 17 denotes a control circuit, which drives the switching element 4 with a predetermined on / off ratio to stabilize the output DC voltage V _O.

The operation of the switching power supply device configured as described above will be described below. First, when the switching element 4 is on, the voltage V _IN is applied to the first choke coil 21 and the voltage V _IN + V _C −V _O is applied to the second choke coil 23. A current that is the sum of the exciting currents of the first choke coil 21 and the second choke coil 23 flows through the switching element 4. The exciting current of the second choke coil 23 flows through the capacitor 6. This period is T _ON .

Next, when the switching element 4 is off, the voltage of each choke coil 21, 23 is inverted and the diode 2
2 conducts. At this time, the voltage V _C is applied to the first choke coil 21 and the voltage V _O is applied to the second choke coil 23. A current that is the sum of the degaussing currents of the first choke coil 21 and the second choke coil 23 flows through the diode 22. Further, the degaussing current of the first choke coil 21 flows through the capacitor 6. This period is T _OFF . In the stable operation state, the magnetic fluxes of the choke coils 21 and 23 are reset in one cycle, so the following equation is established.

V _IN × T _ON = V _C × T _OFF (V _IN + V _C −V _O ) × T _ON = V _O × T _OFF Therefore, the output voltage is as follows.

V _O = V _C = (T _ON / T _OFF ) × V _{IN, that} is, the output voltage V _O can be stabilized by adjusting the on / off ratio of the switching element 4. Figure 1
0 shows the operation waveforms of each part.

Further, since the voltages applied to the choke coils 21 and 23 are equal, the first choke coil 2
It can be seen that the first and second choke coils 23 can be magnetically coupled with the same number of turns. Although detailed description is omitted, this switching power supply device makes the current flowing through the second choke coil 23 an alternating current by making the winding ratio of the first choke coil 21 and the second choke coil 23 equal to its coupling coefficient. It is characterized in that it can be a direct current having no component and the ripple voltage superimposed on the output DC voltage V _O can be 0V.

FIG. 11 shows a circuit configuration diagram in which the switching power supply device is of an input / output insulation type. In FIG. 11, 2
Reference numeral 4 is a transformer, 24a is its primary winding, and 24b is its secondary winding. The configuration is the same as the switching power supply device shown in FIG. 9 except that the transformer 24 is connected instead of the first choke coil 21 in FIG. The operation is similar to that of the switching power supply device of FIG. 9 except that the turns ratio is converted after the secondary winding 24b.

However, a surge voltage due to the leakage inductance of the transformer 24 is generated during switching. Also in this switching power supply device, the transformer 24 and the choke coil 23 can be magnetically coupled, and by making the winding ratio of the secondary winding 24b and the choke coil 23 equal to its coupling coefficient, the current flowing through the choke coil 23 can be converted into an AC component. It has a feature that it can be a direct current that is not present and the ripple voltage that is superimposed on the output DC voltage can be 0V. FIG. 12 shows the operation waveform chart of each part.

[0011]

However, in the above-mentioned conventional configuration, when the current flowing through the choke coil at a light load becomes 0 A, T _ON is shortened in order to stabilize the output voltage. Depending on the output specifications that cause a sudden change in load, the inductance of the choke coil must be set to a large value. When the switching element 4 is turned on, the diode 5 is conducting, so that a recovery current is generated. At this time, the voltage applied to the switching element 4 is rapidly discharged from V _IN + V _O to 0 V, so that a turn-on loss occurs. Occurs. In addition to these,
In the case of the insulation type as described above, there is a problem that a large turn-off loss occurs due to a surge voltage caused by the leakage inductance of the transformer 24 and a loss occurs in the snubber circuit, resulting in a decrease in efficiency. Was there.

The present invention solves the above-mentioned conventional problems, and provides a switching power supply device that suppresses fluctuations in the ON / OFF period of a switching element due to load conditions, improves efficiency by realizing zero-cross switching, and realizes low noise. The purpose is to do.

[0013]

In order to solve this problem, a switching power supply device according to the present invention includes a primary winding of a first transformer having at least a primary winding and one or more secondary windings. A first switching means that repeats on / off is connected in series, and a second switching means and a first capacitor that repeat on / off alternately with the first switching means in parallel with the primary winding of the first transformer. A series circuit is connected, and a series circuit of a primary winding of a second transformer and a second capacitor having at least a primary winding and one or more secondary windings is connected in parallel to the second switching means. The voltage generated in the secondary windings of the first and second transformers is supplied to the output via the rectifying / smoothing means.

[0014]

With this configuration, when the first and second switching means are turned on, the energy stored in the parasitic capacitor of the switching means and the distributed capacitance of the transformer is discharged and then turned on, so that no spike current is generated. When the first and second switching means are turned off, no spike voltage is generated due to the influence of the leakage inductance of the transformer. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed. Furthermore, since the number of turns can be set independently for multiple outputs, the degree of freedom in design is increased, and there is also the effect of improving the regulation characteristics by utilizing the minute voltage fluctuation of the clamp capacitor. Further, the current resonance can achieve zero current switching of the rectifier diode on the secondary side, turn-off recovery does not occur, and the turn-off current of the switching element can be reduced, so that the turn-off switching loss can be reduced. Furthermore, by changing the capacitance values of the two clamp capacitors, it is possible to set the resonance frequency according to the leakage inductance of the two transformers.

[0015]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a switching power supply device according to a first embodiment of the present invention.

Reference numeral 1 is an input DC power supply, and the input voltage is V _IN . 2a-2b are input terminals, 3 is a first transformer, which has a primary winding 3a and one or more secondary windings 3b.
One end of the next winding 3a is connected to the input terminal 2a and the other end is connected to the input terminal 2b via the first switching element 4,
The secondary winding 3b is connected to the first output terminals 13a-13b via the first rectifying diode 11. Reference numeral 4 denotes a first switching element, which is turned on / off by the control circuit 17. Reference numeral 5 denotes a first diode, and the first switching element 4 and the first diode 5 constitute a first switching means.

Reference numeral 6 is a first capacitor for holding the DC voltage V _C1 , 7 is a second switching element, 8 is a second diode, and the second switching element 7
And the second diode 8 constitutes a second switching means. A second capacitor 9 holds the DC voltage V _C2 and is connected to both ends of the switching element 7 via the primary winding 10 a of the second transformer 10. 10 is a second transformer, which is a primary winding 10a and one or more secondary windings 1
0b and the secondary winding 10b has a second rectifier diode 1
4 to the second output terminals 16a-16b.

Reference numeral 11 is a first rectifying diode, and 12
Is a first smoothing capacitor, the first rectifying diode 11 and the first smoothing capacitor 12 constitute a first rectifying and smoothing means, and induces the secondary winding 3b of the first transformer 3. The voltage is rectified and smoothed, and the first output terminal 13a-
Supply voltage to 13b. 13a-13b are first output terminals. 14 is a second rectifier diode, and 15
Is a second smoothing capacitor, and the second rectifying diode 14 and the second smoothing capacitor 15 constitute a second rectifying and smoothing means, and induce the secondary winding 10b of the second transformer 10. Rectifying and smoothing the voltage, the second output terminal 16
Supply voltage to a-16b. 16a-16b are second output terminals. Reference numeral 17 denotes a control circuit which detects the voltage between the second output terminals 16a and 16b and changes the on / off ratio of the first switching element 4 and the second switching element 7 so that the output voltage becomes constant. To occur.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 2, (a) shows the first of the control circuit 17.
Drive pulse waveform V of the switching element 4 of_G1Shows
(B) is the second switching element 7 of the control circuit 17.
Drive pulse waveform V_G2(C) shows the first
Primary winding current I of lance 3_L1And (d) is the
Primary winding current I of the transformer 10 of 2_L2Shows,
(E) is the voltage V applied to the first switching means
_DS1And (f) is the first switching means.
Current I_Q1And (g) is the second switch.
Voltage V applied to the connecting means_DS2And (h)
Is the current I flowing through the second switching means._Q2Shows
(I) is the current I flowing through the first rectifying diode 11.
_D1(J) shows the second rectifier diode 14
Current I _D2Is shown.

In order to show the change in the operating state over time, t₁~ T₃
Is shown in the figure. Time t₁To turn on the control circuit 17
Signal causes the first switching element 4 to turn on and simultaneously
When the switching element 7 of is turned off, the first transformer 3
Input voltage V to the primary winding 3a of _INIs applied simultaneously with the second
Of the voltage V to the primary winding 10a of the transformer 10 of_IN+ V_C1-V
_C2Is applied. At this time, the secondary winding 3 of the first transformer 3
the first rectifying diode 11 and the second rectifying diode 11 connected to b
Second rectification connected to the secondary winding 10b of the transformer 10.
The diode 14 is connected so as to be off.
The current I of the primary winding 3a of the first transformer 3_L1And the second
The current in the primary winding 10a of the transformer 10 increases linearly
And excites the first transformer 3 and the second transformer 10.
Energy is stored.

At time t ₂ , the first off signal of the control circuit 17
When the switching element 4 is turned off, the current flowing through the first switching element 4 turns on the second diode 8. At the same time, the second switching element 7 is turned on by the ON signal of the control circuit 17, but the ON current I _Q2 is
There is no change in operation regardless of whether the current flows through the diode 8 or the second switching element 7. When the second diode 8 or the second switching element 7 is turned on, the DC voltage V _C1 held in the first capacitor 6 is applied to the primary winding 3a of the first transformer 3, and at the same time, the second transformer 10
The DC voltage V _C2 held by the second capacitor 9 is applied to the primary winding 10a of the. At this time, the first transformer 3
First rectifying diode 11 connected to the secondary winding 3b of the
Turns on, and current is supplied to the first output terminals 13a-13b. In addition, the secondary winding 10b of the second transformer 10
The second rectifying diode 14 connected to is also turned on,
Current is also supplied to the second output terminals 16a-16b.

At this time, the current I _Q2 flowing through the second switching means is the first transformer 3 and the second transformer 10.
Gradually decreases as the excitation energy of the first transformer 3 decreases, the output current emitted from the secondary winding 3b of the first transformer 3 increases, and the output current emitted from the secondary winding 10b of the second transformer 10 increases. It will be a negative value. When the second switching element 7 is turned off by the OFF signal of the control circuit 17 while a negative current is flowing in the second switching element 7, this current turns on the first diode 5. At the same time, the first switching element 4 is turned on by the ON signal of the control circuit 17, but the current _IQ1 flowing through the first switching means operates regardless of whether the current _IQ1 flows through the first switching element 4 or the first diode 5. Does not change.
When the first switching element 4 is turned on and at the same time the second switching element 7 is turned off, the input voltage V _IN is applied to the primary winding of the first transformer 3, and at the same time, the second transformer 1 is turned on.
The voltage V _IN + V _C1 −V _C2 is applied to the 0 primary winding 10a. This operation is repeated.

When the ON period of the first switching means is T _ON and the OFF period is T _OFF , V _IN × T _ON = V _C1 × T _OFF is established depending on the reset condition of the first transformer 3, and the second transformer 10 From the reset condition of (V _IN + V _C1 −V _C2 ) × T _ON = V _C2 × T _OFF . When V _C1 and V _C2 are obtained from the above, V _C1 = T _ON / T _OFF × V _IN V _C2 = T _ON / T _OFF × V _IN Primary winding 3a and secondary winding 3 of the first transformer 3
When the turn ratio of b is n ₁ : 1 and the turn ratio of the primary winding 10a and the secondary winding 10b of the second transformer 10 is n ₂ : 1, the output voltage V _{OUT1 of} the first output terminals 13a-13b Is V _OUT1 = V _C1 / n ₁ = T _ON / T _OFF / n ₁ × V _IN The output voltage V _OUT2 of the second output terminals 16a-16b is V _OUT2 = V _C2 / n ₂ = T _ON / T _OFF / n ₂ × V _IN , and an output voltage proportional to V _OUT1 and V _OUT2 is obtained,
The output voltage can be controlled by the on / off ratio of the first switching element 4 and the second switching element 7. In this configuration, the spike voltage at the turn-off of the first switching element 4 and the second switching element 7 due to the leakage inductance of the transformer is effectively turned on by turning on the first diode 5 and the second diode 8. It is absorbed by the first capacitor 6 and the second capacitor 9 and no spike voltage is generated. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed.

Further, since the two outputs are taken out from different transformers, the winding ratio of the transformer can be set individually, and the degree of freedom in design increases. Also, the exciting current of the transformer is reduced, and the inductance value can be relatively increased. This is advantageous in increasing the frequency. Further, the first capacitor 6 and the second capacitor 9 were used for the purpose of holding the DC voltage, but the capacitance value of the capacitor can be reduced to improve the regulation characteristic by varying the DC voltage value within one cycle. Is.

Furthermore, the first transformer 3 and the second transformer 10 can be magnetically coupled, and the number of parts can be reduced. Further, when the transformers are coupled to each other, the winding ratio and coupling coefficient of the primary winding 3a of the first transformer 3 and the primary winding 10a of the second transformer 10 are made equal to each other, so that the first transformer 3 or the second transformer 3 Another feature is that the AC current component of the current flowing through the primary winding of the transformer 10 can be set to zero.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows the configuration of the switching power supply device according to the second embodiment of the present invention.

Reference numeral 1 is an input DC power supply, and the input voltage is V _IN . 2a-2b are input terminals, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b.
Reference numeral 4 denotes a first switching element, which is turned on / off by the control circuit 17. Reference numeral 5 denotes a first diode, and the first switching element 4 and the first diode 5 constitute a first switching means.

Reference numeral 6 is a first capacitor for holding the DC voltage V _CI , 7 is a second switching element, 8 is a second diode, and the second switching element 7
And the second diode 8 constitutes a second switching means. _{Reference numeral} 9 is a second capacitor that holds the DC voltage V _C2 , and 10 is a second transformer, which is the primary winding 10a.
And one or more secondary windings 10b. Reference numeral 11 is a first rectifying diode, 12 is a first smoothing capacitor, and the first rectifying diode 11 and the first smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13a-13b.
Is a first output terminal. Reference numeral 14 is a second rectifying diode, 15 is a second smoothing capacitor, and the second rectifying diode 14 and the second smoothing capacitor 15 make a second
And 16a-16b are second output terminals. Reference numeral 17 denotes a control circuit, which is a second output terminal 16
The voltage between a-16b is detected, and a control signal for changing the on / off ratio of the first switching element 4 and the second switching element 7 is generated so that the output voltage becomes constant.

Reference numeral 18 denotes a third capacitor, which is connected to both ends of the first switching element 4 and suppresses a sharp change in the voltage applied to the first switching element 4 and the second switching element 7. The ON / OFF signal of the control circuit 17 is set so that the first switching element 4 and the second switching element 7 have an OFF period at the same time.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of each part in FIG.

In FIG. 4, (a) shows the first of the control circuit 17.
Drive pulse waveform V of the switching element 4 of_G1Shows
(B) is the second switching element 7 of the control circuit 17.
Drive pulse waveform V_G2(C) shows the first
Primary winding current I of lance 3_L1And (d) is the
Primary winding current I of the transformer 10 of 2_L2Shows,
(E) is the voltage V applied to the first switching means
_DS1And (f) is the first switching means.
Current I_Q1And (g) is the second switch.
Voltage V applied to the connecting means_DS2And (h)
Is the current I flowing through the second switching means._Q2Shows
(I) is the current I flowing through the first rectifying diode 11.
_D1(J) shows the second rectifier diode 14
Current I _D2Is shown.

The basic operation is the same as the circuit configuration of the first embodiment, but the first switching element 4 and the second switching element 7 have an off period at the same time, and the first switching is performed during that period. Element 4 and second switching element 7
It is set so that the voltage applied to is changed. The third capacitor 1 is provided at both ends of the first switching element 4.
Since 8 is connected, the turn-off of the first switching element 4 and the steep rise and fall of the voltage waveform at the time of turn-off are alleviated, and the third capacitor 18
Since the first switching element 4 can be turned on after the charge stored in the input DC power supply 1 is regenerated,
Does not result in the turn-on loss of the switching element 4. The second switching element 7 has a similar effect.

The operations other than the transition are similar to those of the embodiment described with reference to FIG. When these capacitors are added, the output impedance of each winding of the first transformer 3 changes at the time of transition, and especially the initial current value of each winding current when the first switching element 4 is off changes. The influence on the operation itself is small, and since the voltage waveforms applied to the first switching element 4 and the second switching element 7 are not steep, the generation of noise is suppressed, and the first switching element 4 and the second switching element 7 are suppressed. There is an effect that the occurrence of switching loss of the switching element 7 can be suppressed. Further, in this embodiment, the spike voltage at the time of turning off the first switching element 4 and the second switching element 7 due to the leakage inductance of the transformer is effective because the first diode 5 and the second diode 8 are turned on. The first capacitor 6
And it is absorbed by the second capacitor 9 and no spike voltage is generated. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed.

Further, since the two outputs are taken out from different transformers, the winding ratio of the transformer can be set individually, and the degree of freedom in design is increased. Also, the exciting current of the transformer is reduced, and the inductance value can be relatively increased. This is advantageous in increasing the frequency. Further, the capacitors 6 and 9 were used for the purpose of holding the DC voltage, but it is possible to improve the regulation characteristic by reducing the capacitance value of the capacitors and changing the DC voltage value within one cycle.

Further, the first transformer 3 and the second transformer 10 can be magnetically coupled, and the number of parts can be reduced. Further, when the transformers are coupled to each other, the winding ratio and coupling coefficient of the primary winding 3a of the first transformer 3 and the primary winding 10a of the second transformer 10 are made equal to each other, so that the first transformer 3 or the second transformer 3 Primary winding 10a of the transformer 10
There is also a feature that the AC current component of the current flowing through can be made zero.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 shows the configuration of a switching power supply device according to the third embodiment of the present invention.

Reference numeral 1 is an input DC power supply, and the input voltage is V _IN . 2a-2b are input terminals, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b.
Reference numeral 4 denotes a first switching element, which is turned on / off by the control circuit 17. Reference numeral 5 denotes a first diode, and the first switching element 4 and the first diode 5 constitute a first switching means.

Reference numeral 6 is a first capacitor for holding the DC voltage V _C1 , 7 is a second switching element, 8 is a second diode, and the second switching element 7 is provided.
And the second diode 8 constitutes a second switching means. _{Reference numeral} 9 is a second capacitor that holds the DC voltage V _C2 , and 10 is a second transformer, which is the primary winding 10a.
And one or more secondary windings 10b. Reference numeral 11 is a first rectifying diode, 12 is a first smoothing capacitor, and the first rectifying diode 11 and the first smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13a
-13b is a first output terminal. 14 is a second rectifying diode, 15 is a second smoothing capacitor,
The second rectifying diode 14 and the second smoothing capacitor 15 constitute a second rectifying and smoothing means, and 16a-1
6b is a second output terminal. Reference numeral 17 denotes a control circuit, which detects the voltage between the second output terminals 16a and 16b and keeps the output voltage constant by the first switching element 4
And a control signal for changing the on / off ratio of the second switching element 7.

Reference numeral 19 denotes a leakage inductance or an inductance element, which is the primary winding 3 of the first transformer 3.
An output current that is connected in series with a and resonates with the first capacitor 6 during the ON period of the second switching element 7 and is transmitted to the secondary winding 3b of the first transformer 3 is used as a resonance current. . Reference numeral 20 denotes a leakage inductance or an inductance element, which is connected in series to the primary winding 10a of the second transformer 10 and is connected to the second switching element 7
The output current that resonates with the second capacitor 9 during the ON period and is transmitted to the secondary winding 10b of the second transformer 10 is the resonance current.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 6, (a) shows the first of the control circuit 17.
Drive pulse waveform V of the switching element 4 of_G1Shows
(B) is the second switching element 7 of the control circuit 17.
Drive pulse waveform V_G2(C) shows the first
Primary winding current I of lance 3_L1And (d) is the
Primary winding current I of the transformer 10 of 2_L2Shows,
(E) is the voltage V applied to the first switching means
_DS1And (f) is the first switching means.
Current I_Q1And (g) is the second switch.
Voltage V applied to the connecting means_DS2And (h)
Is the current I flowing through the second switching means._Q2Shows
(I) is the current I flowing through the first rectifying diode 11.
_D1(J) shows the second rectifier diode 14
Current I _D2Is shown. Changes in operating conditions over time
T to indicate₁~ T_FourIs shown in the figure.

The basic operation is the same as that of the circuit configuration of the first embodiment, but when the second switching element 7 is turned on and a current is supplied to the output, the first capacitor 6 and the leakage inductance or inductance element are operated. Since 19 resonates and the resonance frequency is set to be sufficiently small,
The secondary winding current I _D1 of the transformer 3 becomes sinusoidal, rises from zero, and becomes zero again at t ₄ . Therefore, the first rectifying diode 11 becomes zero current switching, and recovery does not occur. Similarly, the second capacitor 9 and the leakage inductance or the inductance element 20 resonate, and the resonance frequency is set to be sufficiently small.
The secondary winding current I _D2 of the transformer 10 becomes sinusoidal, rises from zero, and becomes zero again at t ₂ . Therefore the second
The rectifying diode 14 of becomes a zero current switching, and recovery does not occur.

The operation other than the transition is similar to that of the embodiment described with reference to FIG.

Furthermore, the turn-off currents of the first switching element 4 and the second switching element 7 can be reduced, and the switching loss can be reduced.

The DC voltages V _C1 and V _C2 are actually the sum voltage of the DC voltage component and the fluctuation component which is the resonance voltage, but the fluctuation component due to the resonance voltage can be set to a sufficiently small value, so the conversion ratio of the input voltage and the output voltage is Almost the same as the case of the first embodiment.

Further, in the present embodiment, the spike voltage at the time of turning off the first switching element 4 and the second switching element 7 due to the leakage inductance of the transformer causes the first diode 5 and the second diode 8 to turn on. Is effectively absorbed by the first capacitor 6 and the second capacitor 9, and no spike voltage is generated. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed.

Further, since the two outputs are taken out from different transformers, the winding ratio of the transformer can be set individually, and the degree of freedom in design is increased. Also, the exciting current of the transformer is reduced, and the inductance value can be relatively increased. This is advantageous in increasing the frequency. Further, the first capacitor 6 and the second capacitor 9 were used for the purpose of holding the DC voltage, but the capacitance value of the capacitor can be reduced to improve the regulation characteristic by varying the DC voltage value within one cycle. Is. The resonance frequency of the resonance current flowing through the secondary winding of each transformer is the same as that of the first transformer 6 and the leakage inductance or the inductance element 1 in the first transformer 3.
9, the second transformer 10 and the second capacitor 9 and the leakage inductance or the inductance element 20 can be set, and the resonance frequency can be easily set.

Furthermore, the first transformer 3 and the second transformer 10 can be magnetically coupled, and the number of parts can be reduced. Further, when the transformers are coupled to each other, the winding ratio and coupling coefficient of the primary winding 3a of the first transformer 3 and the primary winding 10a of the second transformer 10 are made equal to each other, so that the first transformer 3 or the second transformer 3 Primary winding 10a of the transformer 10
There is also a feature that the AC current component of the current flowing through can be made zero.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 7 shows the configuration of a switching power supply device according to the fourth embodiment of the present invention.

Reference numeral 1 is an input DC power supply, and the input voltage is V _IN . 2a-2b are input terminals, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b.
Reference numeral 4 denotes a first switching element, which is turned on / off by the control circuit 17. Reference numeral 5 denotes a first diode, and the first switching element 4 and the first diode 5 constitute a first switching means.

6 is a first capacitor for holding the DC voltage V _C1 , 7 is a second switching element, 8 is a second diode, and the second switching element 7
And the second diode 8 constitutes a second switching means. _{Reference numeral} 9 is a second capacitor that holds the DC voltage V _C2 , and 10 is a second transformer, which is the primary winding 10a.
And one or more secondary windings 10b. Reference numeral 11 is a first rectifying diode, 12 is a first smoothing capacitor, and the first rectifying diode 11 and the first smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13a
-13b is a first output terminal. 14 is a second rectifying diode, 15 is a second smoothing capacitor,
The second rectifying diode 14 and the second smoothing capacitor 15 constitute a second rectifying and smoothing means, and 16a-1
6b is a second output terminal. Reference numeral 17 denotes a control circuit, which detects the voltage between the second output terminals 16a and 16b and keeps the output voltage constant by the first switching element 4
And a control signal for changing the on / off ratio of the second switching element 7.

Reference numeral 19 denotes a leakage inductance or an inductance element, which is the primary winding 3 of the first transformer 3.
An output current that is connected in series with a and resonates with the first capacitor 6 during the ON period of the second switching element 7 and is transmitted to the secondary winding 3b of the first transformer 3 is used as a resonance current. . Reference numeral 20 denotes a leakage inductance or an inductance element, which is connected in series to the primary winding 10a of the second transformer 10 and is connected to the second switching element 7
The output current that resonates with the second capacitor 9 during the ON period and is transmitted to the secondary winding 10b of the second transformer 10 is the resonance current.

Reference numeral 18 is a third capacitor, which is the first capacitor.
Connected to both ends of the switching element 4 of the first switching element 4 and the second switching element 7
It suppresses abrupt changes in the voltage applied to. The first
Switching element 4 and the second switching element 7
The ON / OFF signal of the control circuit 17 is set so as to have an OFF period at the same time.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 8, (a) shows the first of the control circuit 17.
3 shows a drive pulse waveform V _G1 of the switching element 4 of FIG.
Drive pulse waveform V _G2 of the first transformer 3 is shown, (c) shows the primary winding current I _L1 of the first transformer 3, and (d) shows the primary winding current I _L2 of the second transformer 10. Shows,
(E) is the voltage V applied to the first switching element 4.
_DS1 is shown, (f) shows the current _IQ1 flowing through the first switching means, (g) shows the voltage V _DS2 applied to the second switching means, and (h).
_{Represents the} current I _Q2 flowing in the second switching means, and (i) represents the current I _Q flowing in the first rectifying diode 11.
_D1 is shown, and (j) shows the current I _D2 flowing through the second rectifying diode 14.

The basic operation is the same as the circuit configuration of the third embodiment, but the first switching element 4 and the second switching element 7 have an off period at the same time, and the first switching is performed during that period. Element 4 and second switching element 7
It is set so that the voltage applied to is changed. The third capacitor 1 is provided at both ends of the first switching element 4.
Since 8 is connected, the turn-off of the first switching element 4 and the steep rise and fall of the voltage waveform at the time of turn-off are alleviated, and the third capacitor 18
Since the first switching element 4 can be turned on after the charge stored in the input DC power supply 1 is regenerated, the turn-on loss of the first switching element 4 does not occur. The second switching element 7 has a similar effect.

The operation other than the transition is similar to that of the embodiment described with reference to FIG. When these capacitors are added, the output impedance of each winding of the first transformer 3 changes at the time of transition, and especially the initial current value of each winding current when the first switching element 4 is off changes. There is little effect on the operation itself, in addition to the effect of making the secondary winding current waveform a resonance current,
First switching element 4 and second switching element 7
Since the voltage waveform applied to is not steep, it is possible to suppress the generation of noise and the switching loss of the first switching element 4 and the second switching element 7.

Further, in this embodiment, the spike voltage at the time of turning off the first switching element 4 and the second switching element 7 due to the leakage inductance of the transformer causes the first diode 5 and the second diode 8 to turn on. Is effectively absorbed by the first capacitor 6 and the second capacitor 9, and no spike voltage is generated. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed.

Further, since the two outputs are taken out from different transformers, the winding ratio of the transformer can be set individually, and the degree of freedom in design increases. Also, the exciting current of the transformer is reduced, and the inductance value can be relatively increased. This is advantageous in increasing the frequency. Further, the first capacitor 6 and the second capacitor 9 were used for the purpose of holding the DC voltage, but the capacitance value of the capacitor can be reduced to improve the regulation characteristic by varying the DC voltage value within one cycle. Is. The resonance frequency of the resonance current flowing through the secondary winding of each transformer is the same as that of the first transformer 6 and the leakage inductance or the inductance element 1 in the first transformer 3.
9, the second transformer 10 and the second capacitor 9 and the leakage inductance or the inductance element 20 can be set, and the resonance frequency can be easily set.

Furthermore, the first transformer 3 and the second transformer 10 can be magnetically coupled, and the number of parts can be reduced. Further, when the transformers are coupled to each other, the winding ratio and coupling coefficient of the primary winding 3a of the first transformer 3 and the primary winding 10a of the second transformer 10 are made equal to each other, so that the first transformer 3 or the second transformer 3 Another feature is that the AC current component of the current flowing through the primary winding of the transformer 10 can be set to zero.

[0062]

With this configuration, when the first and second switching means are turned on, the energy stored in the parasitic capacitor of the switching means and the distributed capacitance of the transformer is discharged and then turned on, so that no spike current is generated. At the time of turning off the first and second switching means, no spike voltage is generated due to the influence of the leakage inductance of the transformer. Further, the current of the transformer is always continuous, and fluctuations in the on / off period of the switching element due to load conditions can be suppressed. Furthermore, the number of turns can be set independently for multiple outputs, increasing the degree of freedom in design. It also has the effect of improving the regulation characteristics by utilizing the minute voltage fluctuations of the clamp capacitor. Further, the current resonance can achieve zero current switching of the rectifier diode on the secondary side, turn-off recovery does not occur, and the turn-off current of the switching element can be reduced, so that the turn-off switching loss can be reduced. Furthermore, by changing the capacitance value of the two clamp capacitors,
The resonance frequency can be set according to the leakage inductances of the two transformers.

Therefore, the present invention realizes a small size, high efficiency, and low noise switching power supply device.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a switching power supply device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing operation waveforms of the circuit configuration diagram of FIG.

FIG. 3 is a circuit configuration diagram showing a switching power supply device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing operation waveforms in the circuit configuration diagram of FIG.

FIG. 5 is a circuit configuration diagram showing a switching power supply device according to a third embodiment of the present invention.

6 is an explanatory diagram showing operation waveforms of the circuit configuration diagram of FIG.

FIG. 7 is a circuit configuration diagram showing a switching power supply device according to a fourth embodiment of the present invention.

8 is an explanatory diagram showing operation waveforms of the circuit configuration diagram of FIG. 7.

9 is a circuit configuration diagram of a switching power supply device in the conventional example of FIG.

10 is an explanatory diagram showing operation waveforms of the circuit configuration diagram of FIG. 9.

FIG. 11 is a circuit configuration diagram of a switching power supply device according to a second conventional example.

12 is an explanatory diagram showing operation waveforms of the circuit configuration diagram of FIG. 11.

[Explanation of symbols]

 1 Input DC power supply 2a-2b Input terminal 3 1st transformer 4 1st switching element 5 1st diode 6 1st capacitor 7 2nd switching element 8 2nd diode 9 2nd capacitor 10 2nd Transformer 11 1st rectifying diode 12 1st smoothing capacitor 13a-13b 1st output terminal 14 2nd rectifying diode 15 2nd smoothing capacitor 16a-16b 2nd output terminal 17 Control circuit 18 3rd capacitor 19 Leakage inductance or inductance element 20 Leakage inductance or inductance element 21 First choke coil 22 Diode 23 Second choke coil 24 Transformer

Claims (5)

[Claims] 1. A primary winding of a first transformer having at least a primary winding and one or more secondary windings, and a first switching means that repeats on and off are connected in series,
A series circuit of a first capacitor and a second switching means that alternately repeats ON / OFF alternately with the first switching means is connected in parallel to the primary winding of the transformer, and at least 1 is connected in parallel to the second switching means. A secondary winding of a second transformer having a secondary winding and one or more secondary windings, and a second
A switching power supply device which is connected to a series circuit of the capacitors and supplies the voltage generated in the secondary windings of the first and second transformers to the output through rectifying and smoothing means. 2. A capacitor is connected to both ends of the first switching means or both ends of the second switching means or both, and both the first switching means and the second switching means have a period of being off. 2. The switching power supply device according to claim 1, wherein the switching power supply device is alternately turned on and off. 3. A primary winding of a first transformer having at least a primary winding and one or more secondary windings, and a first switching means that repeats on and off are connected in series,
A series circuit of a first capacitor and a second switching means that alternately repeats ON / OFF alternately with the first switching means is connected in parallel to the primary winding of the transformer, and at least 1 is connected in parallel to the second switching means. A secondary winding of a second transformer having a secondary winding and one or more secondary windings, and a second
Connected to a series circuit of the capacitors, supplies the voltage generated in the secondary windings of the first and second transformers to the output through rectifying and smoothing means, and connects the first transformer or the second transformer.
First and second capacitors, a rectifying / smoothing means, and a second coil, which are coupled to each other through a primary winding and a secondary winding of the transformer.
In the loop composed of the switching means, the capacitor or the rectifying / smoothing means or a combination thereof resonates with the leakage inductance of the first and second transformers or the external inductance, and the first or second transformer or both of them. Switching power supply device in which the secondary winding current is used as a resonance current. 4. A capacitor is connected to both ends of the first switching means, both ends of the second switching means, or both, and both the first switching means and the second switching means have a period of being off. The switching power supply device according to claim 3, wherein the switching power supply device is alternately turned on and off. 5. The switching power supply device according to claim 1, claim 2, claim 3, claim 4 or claim 5, wherein the first transformer and the second transformer are magnetically coupled.